The IP phone at the gate sendings a URL request when dialed which actives the trigger... it is getting the message and triggering at the output but the iframe doesnt change??
I did a search here and couldn't see anything that was relevant
You appear to be sending a url in msg.payload, but if you look at the help text for node-red-node-ui-iframe (assuming that is what you are using) then it says
" The URL of a web page to embed can be specified in the settings menu or by the url property of an input message."
That says you have to pass the url in msg.url, not msg.payload.